/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.camunda.bpm.extension.reactor.projectreactor.io.codec.json;

import static java.util.Objects.requireNonNull;

import java.io.IOException;
import java.util.function.Consumer;
import java.util.function.Function;

import org.camunda.bpm.extension.reactor.projectreactor.io.buffer.Buffer;
import org.camunda.bpm.extension.reactor.projectreactor.io.codec.BufferCodec;
import org.camunda.bpm.extension.reactor.projectreactor.io.codec.Codec;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * A codec for decoding JSON into Java objects and encoding Java objects into JSON.
 *
 * @param <IN>  The type to decode JSON into
 * @param <OUT> The type to encode into JSON
 * @author Jon Brisbin
 */
public class JsonCodec<IN, OUT> extends BufferCodec<IN, OUT> {

  private final Class<IN> inputType;
  private final ObjectMapper mapper;

  /**
   * Creates a new {@code JsonCodec} that will create instances of {@code inputType}  when
   * decoding.
   *
   * @param inputType The type to create when decoding.
   */
  public JsonCodec(Class<IN> inputType) {
    this(inputType, null);
  }

  /**
   * Creates a new {@code JsonCodec} that will create instances of {@code inputType}  when
   * decoding. The {@code customModule} will be registered with the underlying {@link
   * ObjectMapper}.
   *
   * @param inputType    The type to create when decoding.
   * @param customModule The module to register with the underlying ObjectMapper
   */
  @SuppressWarnings("unchecked")
  public JsonCodec(Class<IN> inputType, Module customModule) {
    this(inputType, customModule, Codec.DEFAULT_DELIMITER);
  }

  /**
   * Creates a new {@code JsonCodec} that will create instances of {@code inputType}  when
   * decoding. The {@code customModule} will be registered with the underlying {@link
   * ObjectMapper}.
   *
   * @param inputType    The type to create when decoding.
   * @param customModule The module to register with the underlying ObjectMapper
   * @param delimiter    A nullable delimiting byte for batch decoding
   */
  @SuppressWarnings("unchecked")
  public JsonCodec(Class<IN> inputType, Module customModule, Byte delimiter) {
    super(delimiter);
    requireNonNull(inputType, "inputType must not be null");
    this.inputType = inputType;

    this.mapper = new ObjectMapper();
    if (null != customModule) {
      this.mapper.registerModule(customModule);
    }
  }

  @Override
  @SuppressWarnings("unchecked")
  protected IN doBufferDecode(Buffer buffer) {
    try {
      if (JsonNode.class.isAssignableFrom(inputType)) {
        return (IN) mapper.readTree(buffer.inputStream());
      } else {
        return mapper.readValue(buffer.inputStream(), inputType);
      }
    } catch (IOException e) {
      throw new IllegalStateException(e);
    }
  }

  @Override
  public Function<Buffer, IN> decoder(Consumer<IN> next) {
    return new JsonDecoder(next);
  }

  private class JsonDecoder implements Function<Buffer, IN> {
    private final Consumer<IN> next;

    private JsonDecoder(Consumer<IN> next) {
      this.next = next;
    }

    @SuppressWarnings("unchecked")
    @Override
    public IN apply(Buffer buffer) {
      return doDelimitedBufferDecode(next, buffer);
    }
  }

  @Override
  public Buffer apply(OUT out) {
    try {
      return addDelimiterIfAny(new Buffer().append(mapper.writeValueAsBytes(out)));
    } catch (JsonProcessingException e) {
      throw new IllegalStateException(e);
    }
  }

}
